Sound translating device



July 7, 1942. c, pyE 2,288,839

SOUND TRANSLATING DEVICE Filed NOV. 2'7, 1959 5 Sheacfi Shefit 1INVENTOR ATTORNEYS July 7, 1942. H. c. PYE' SOUND TRANSLATING DEVICEFiled Nov. 27, 1939 3 Sheets-Sheet 2 INVENTORQ Harold C Pye BY ATTORNEYSJuly 7, 1942.

, H. C. PYE

SOUND TRANSLATING'DEVICE 3 Sheets-Sheet 3 Filed Nov. 27, 1939 .QBm SQ Imotmb wk Patented July 7, 1942 NT OFFICE SOUND TRANSLATING DEVICE HaroldC. Pye, Oak Park, Ill., assignor to Associated Electric Laboratories,Inc., Chicago, 111., a

corporation of Delaware Application November 27, 1939, Serial No.306,287

4 Claims. (Cl. 179-122) The present invention relates to soundtranslating devices and more particularly'to telephone transmitters.

A conventional telephone transmitter is responsive to sound waves ofdifferent frequencies disposed within the audible frequency range andincluding background sound waves having frequencies disposed within afirst band in the audible range and signal ound waves having frequenciesdisposed within a second band in the audible range. Ordinarily, thebackground sounds or noises have frequencies disposed toward the lowerend of the audible range; 'while the signal sounds have frequenciesdisposed toward the higher end of the audible range. Consequently, thetelephone transmitter transmits sou: 0. energy corresponding both to thebackground noises and to the signal sounds; thereby to cause a telephonereceiver associated with the telephone transmitter to reproduce both thebackground noises and the signal sounds.

Accordingly, it is an object of the present invention to provide atelephone transmitter embodying an improved arrangement for preventingthe transmitter from transmitting sound energy corresponding to thebackground noises.

Another object of the invention is to provide in a transmitter, animproved mechanical filter arrangement for filtering out undesirablenoises having frequencies disposed within a predetermined frequency bandin the audible frequency range of the transmitter.

Another object of the invention is to provide in a sound translatingdevice having a predetermined inherent acoustical response over a givenfrequency range, an improved mechanical filter arrangement for alteringthe effective acoustical response of the device over a given frequencyband within the given frequency range.

A further object of the invention is to provide a sound translatingdevice which is of extremely simple and rugged construction, which iscompact and economical to manufacture and which is efficient inoperation.

In general, the objects set forth above are in part realized inaccordance with the present invcntion by p oviding a sound translatingdevice in the form of a telephone transmitter which comprises asubstantially cup-shaped casing, a

vibratory diaphragm, means for securing the being resiliently connectedto the casing and movable with respect thereto, and a movable mechanicalsystem coupled to the second electrode. During the operation of thetransmitter the vibratory diaphragm is subjected to sound waves havingdifferent frequencies in the audible range including background soundwaves having frequencies disposed in a first band in the audible rangeand signal sound waves to be transmitted having frequencies disposed ina second band in the audible range, whereby the sound energy transmittedby the transmitter corresponds to the relative movement between theelectrodes, the movable mechanical system constitutes means forfiltering out the background sound energy. More particularly, themechanical system comprises mass and stillness characteristics which areso proportioned and related that the second electrode is moved with thefirst electrode when the diaphragm is subjected to the sound waveshaving frequencies disposed in the first band i the audible range.

Two modifications of the movable mechanical system are disclosed. Inaccordance with one modification, the movable mechanical system iscommonly coupled to the first and second elec trodes, whereby therelative movement between the first and second electrodes is controlled,the system being arranged in the casing and including a number of massrings and a numberof connecting stiffness rings constructed and arrangedto provide a bellows construction extending between the first and secondelectrodes. In accordance with the other modification, the movablemechanical system is commonly coupled to the second electrode and thecasing, whereby the relative movement between the second electrode andthe casing is controlled, the system being arranged in the casing andincluding a number of mass rings and a number of stiffness ringsconstructed and arranged to provide a bellows construction extendingbetween the second electrode and the casing.

More particularly the transmitter comprises an impedance element in theform of a charge of carbon granules disposed between the first andsecond electrodes, whereby relative movement between the first andsecond electrodes is effective to control the effective impedance of theimpedance element such that the variation in effective impedance of theimpedance element corresponds to sound energy to be transmitted by thetransmitter.

Further, it is noted that the transmitter has a predetermined inherentacoustical response over the audible frequency range and that themovable mechanical system constitutes a mechanical filter forestablishing a cut-off point disposed Within the audible range, wherebythe effective acoustical response of the device is a substantiallynegligible value on one side of the cut-off point and an appreciablevalue on the other side of the cut-off point, wherein the location ofthe cut-off point within the audible range is determined by both themass and stiffness characteristics of the system. Finally, it is notedthat the effective acoustical response of the transmitter is asubstantially negligible value on the side of the cut-off point disposedtoward the low frequency end of the audible range and an appreciablevalue on the side of the cut-off point disposed toward the highfrequency end of the audible range, whereby the transmitter is effectiveto transmit sound energy corresponding only to relatively high frequencysignal sounds.

Further features of the invention pertain to the particular constructionand arrangement of the elements of the sound translating device, wherebythe above-outlined and additional op erating features are attained.

The novel features believed to be characteristic of the invention areset forth with particularity in the appended claims. The invention, bothas to its organization and method of operation, together with furtherobjects and ad.- vantages thereof, will best be understood by referenceto the following specification taken in connection with theaccompanyingdrawings, in which Figure 1 is a plan view of one form of soundtranslating device embodying the present invention; Fig. 2 is alongitudinal sectional view of the device taken along the line 2-2 inFig. 1; Fig. 3 is a plan view of a modified form of sound translatingdevice embodying the present invention; Fig. 4 is a longitudinalsectional view of the device taken along the line 4-4 in Fig. 3; andFig. 5 is a graphic illustration of the performance characteristics ofsound translating devices of the types illustrated in Figs. 1. 2 and 3,4.

Referring now more particularly to Figs. 1 and 2 of the drawings, thereis illustrated a preferred embodiment of a sound translatin device inthe form of a telephone transmitter H) which comprises a substantiallycup-shaped housing H including a flat bottom wall l2, a central dome l3,a cylindrical side wall M, an annular flange l5 and a cylindrical sidewall IS. the flange l5 bein disposed between the side walls l4 and I6.Prefably, the housing H is formed of a suitable aluminum alloy in orderto obtain a rigid lightweight mounting for the elements of thetransmitter and supports a suitable mouthpiece, not shown. An annularface plate I! is arranged within the sidewall N5 of the housing II andretained in place by an annular flange l8 spun from the side wall l6into enga ement with the face plate Preferably the face plate I! isformed of a suitable aluminum alloy and is provided with a number ofopenings |9 therein arranged in a circular pattern in ord r to permitsound waves to enter the housing H. An annular groove 20 is provided inthe cylindrical side wall of the face plate I! in order to provide aresilient gripping action between the side wall of the face plate I1 andthe side wall 56 of the housing II when the annular flange I8 is spunfrom the side wall l6 into engagement with the face plate H.

The housing ll encloses a moving a thin cushioning ring 28 formed ofinsulating material is disposed between the flange 25 carried by theprimary diaphragm 2| and the annular shoulder 21 provided on the faceplate l1. Finally the front wall of the primary diaphragm 2| is coveredwith a moisture-proof protective covering 29.

The casing element 23 comprises a substantially central dome 30 and awide annular flange 3|. Finally the secondary diaphragm 22 comprises anannular ring disposed between .the annular flange 25 carried by theprimary diaphragm 2| and the annular flange 3| carried by the easingelement 23; the inner periphery of the secondary diaphragm 22 beingsuitably secured to the annular flange 3| and the outer periphery of thesecondary diaphragm 22 being suitably secured to the annular flange 25.The center of the dome 24 carried by the primary diaphragm 2| is securedto the center of the dome 30 carried by the casing element 23 by aneyelet or rivet 32,- thus forming a composite diaphragm assembly whichis very stiff over the central conical portion and extremely flexibleover the outer edge flange portion. Also it is noted that the eyelet 32has an opening 33 provided therein in order to provide a breathingaction between the interior of the casing element 23 and the outsideatmosphere. Also, the telephone transmitter I0 comprises a casingelement 34 includ-*- ing a substantially central dome 35 and a wideannular flange 36, the dome 35 carried by the casing element 34 beingarranged within the of thin duralumin sheet metal in order to obtain thecombination of light weight parts having high tensile strength.

A ring-shaped electrode 38 is suitably secured to the annular flange 3|carried by the casing element 23 adjacent the dome 30 thereof;similarly,

a ring-shaped electrode 39 is' suitably secured to the annular flange 36carried by the casing element 34 adjacent the dome 35 thereof.Preferably, the electrodes 38 and 39 are formed of solid carbon and aresealed with respect to each other by an annular corrugated flexiblepaper bellows 40 extending therebetwe'enand cemented thereto. Further itis noted that a charge of carbon granules. not shown, is arranged withinthe domes 30 and 35 of the casing elements 23 and 34, respectively, andextends between the electrodes 38 and 39, the interior surfaces of thedomes 39 and 35 respectively carried by the casing elements 23 and 34being varnished in order to electrically insulate the casing elements 23and 34 from the charge of carbon granules disposed spectively secured tothe annular flanges 3| and 38 respectively carried by the casingelements 23 and 34; while theinsulating rings 44 and 45 are respectivelysecured between the metallic rings 4|, 42 and 42, 43, thereby to providea bellows construction surrounding the electrodes 33 and 39 andextending between the annular flanges 3| and 36.

The bottom wall l2 of the housing carries an electrical terminal 46electrically connected thereto and an electrical terminal 41electrically insulated therefrom, the terminal 41 being electricallyconnected by a flexible conductor 48 to a plug 49 carried by the dome 35of the casing element 34. Accordingly the terminal 49, the housing II,the primary diaphragm 2|, the casing element 23 and the electrode 38 arearranged in series circuit relation; while the terminal 41, theconductor 48, the plug 49 the casing element 34 and the electrode 39 arearranged inseries circuit relation, the charge of carbon granules beingdisposed between the electrodes 38 and 39.

During the operation of the telephone transmitter the charge of carbongranules disposed between the electrodes 38 and 39 is variablycompressed in accordance with the relative movements between theelectrodes 38 and 39, thereby to vary the electrical impedance orresistance of the circuit extending between the terminals 48 and 41.

Also during operation of the telephone transmitter Ill, movement of theprimary diaphragm 2 I, and consequently movement of the casing element23, is damped by the action of a resonance chamber 58 formed between theprimary diaphragm 2| and the face plate l1; movement of the casingelement 34 is damped by the resilient bellows 31; while movement of thecasing element 23 with respect to the casing element 34 is damped by theresilient bellows 40 and bythe breathing action of the air passingthrough the opening 33 formed in the eyelet 32 incident to movement ofthe casing elements 23 and 34 with respect to each other.

Finally it is noted that the movements of the casing elements 23 and 34with respect to each other, and consequently the movements of theelectrodes 38 and 39 with respect to each other, are controlled by themechanical low-pass filter arrangement disposed between the annularflanges 3| and respectively carried by the casing elements23 and 34.

More particularly, at lowfrequencies, the mechanical low-pass filterarrangement constitutes in effect a substantially rigid connectionbetween the annular flanges 3| and 36 respectively carried by the casingelements 23 and 34, thereby to cause the movements of the casingelements 23 to be transmitted directly to the casing element 34.Accordingly, at low frequencies, the electrodes 38 and 39 are not movedsubstantially with respect to each other. Hence the mechanical lowpassfilter arrangement prevents low frequency sound energy from beingtransmitted from the telephone transmitter or filters out low frequencysound energy. On the other hand, at high frequencies, the mechanicallow-pass filter arrangement constitutes in effect no connection betweenthe annular flanges 3| and 38 respectively carried by the casingelements 23 and 34, thereby to cause the casing element 23 to move withrespect to the casing element 34. Accordingly, at high frequencies, theelectrodes 38 and 39 are moved substantially with respect to each other.Hence the mechanical low-pass filter arrangement does not prevent highfrequency sound energy from being transmitted from the telephonetransmitter or permits high frequency sound energy to pass.

.From the above description of the mode of operation of the mechanicallow-pass filter arrangement commonly associated with the casing elements23 and 34 it will be understood that the telephone transmitter iseffective to transmit at substantial magnitudes only sound energy havinga frequency disposed above a given cut-off frequency.

Further it will be understood that the point of cut-off of the telephonetransmitter i may be controlled by varying the mass of the metallicrings 4|, 42 and 43 and by varying the stiffness of the insulating rings44 and 45. More particularly, by increasing the stiffness of theinsulating rings 44 and 45 or.by decreasing the mass of the metallicrings 4|, 42 and 43, the point of cut-off of the telephone transmitterl0 may be shifted from a given frequency band to a higher frequencyband; on the other hand, by decreasing the stiffness of the insulatingrings 44 and 45 or by increasing the mass of the metallic rings 4|,42-and 43, the point of cut-off of the telephone transmitter I! may beshifted from a given frequency band to a lower frequency band. Furtherit will be understood that any reasonable number of insulating rings andmetallic rings may be provided in the telephone transmitter l0, and thatthe number of insulating rings and metallicrings provided will not alonecontrol the point of cut-off of the telephone transmitter l9, as thepoint of cut-off of the telephone transmitter will be determined by theratio between the composite mass of the metallic rings and the compositestiffness of the insulating rings.

The construction and arrangement of the sound translating device shownin Figs. 1 and 2 are disclosed. and claimed in the copending-divisionalapplication of Harold C. Pye, Serial No. 413,184, filed October 1, 1941.

Referring now more particularly to Figs. 3 and 4 of the drawings thereis illustrated a modified embodiment of a sound translating device inthe form of a telephone transmitter of the same general construction andarrangement as the telehpone transmitter l8, previously described. Moreparticularly, the telephone transmitter 68 comprises a housing 6|including a flat bottom wall 92, a cylindrical side wall 63, an annularfiange G4 and a cylindrical side wall 65, the flange 84 being disposedbetween the side walls 83 and 85. Further the telephone transmitter 69comprises a face plate 86', a diaphragm assembly 61'. two casingelements 88 and S9 and two electrodes 19 and T1 constructed and arranged in the general manner previously explained. Further it is notedthat the casing element 88, includes a centrally disposed dome 12 anda'narrow annular flange 13; while the casing element 89 includes acentrally disposed dome 14 and a wide annular flange 15, the electrodes19 and 1| being respectively secured to the annular flanges 13 and 15respectively carried by the casing elements 68 and 69 adjacent the domesthereof, and an annular corrugated resilient paper bellows 16 beingcemented to the electrodes 70 and II.

In the telephone transmitter 60 a mechanical lcw-pass filter arrangement,is commonly associated with the casing element 69 and the bottom wall62 of the housing 6| which comprises fivemetallic rings ll; l8, i9, 80and 8!, four rings of insulating material 82, 83,-84 and 85 and ametallic disk 86. More particularly, the metallic disk 86-is rigidlysecured-toan electrical terminal 8'! carried by the bottom wall 62 ofthe housing 6| and electrically insulated therefrom; while the metallicrings TI and 8| are respectively secured to the flange carried by thecasing element 69 and the disk 86. The insulating rings 62 and 85 arerespectively secured to the metallic rings and 8| and to the metallicrings 76 and Bil; while the insulating rings 33 and M are respectivelysecured to the metallic rings 78, it and i9, 80. Finally an annularcorrugated flexible paper bellows 86 is arranged between the insulatingring 85 and the disk 86.

Also the bottom wall 62 of the housing 6! carries an electrical terminal89 electrically con,- nected thereto; while the electrical terminal 8]is electrically connected to a plug 90 carried by the casing element titby a flexible conductor 6!. Hence, the terminal 39 is electricallyconnected by way of the housing M, the diaphragm assembly 6i and thecasing element 68 to the electrode Vii; while the terminal 87 iselectrically connected by way of the conductor M, the plug 90 and thecasing element $8 to the electrode "ii, a charge of carbon granulesbeing disposed between the electrodes m and H.

During operation of the telephone transmitter 68 movement of thediaphragm assembly 611, and consequently movement of the casing element68, is damped by the action of a resonance chamber 92 formed between thediaphragm assembly 61 and the face plate @6; movement of the casingelement 69 is damped by the resilient bellows 88; while movement of thecasing element 68 with respect to the casing element 69 is clamped bythe resilient bellows I6 and by the breathing action of the air passingthrough the opening formed in the eyelet incident to movement of thecasing elements 68 and 69 with respect to each other.

Finally it is noted that the movements of the casing element 69 withrespect to the bottom wall 62 of the housing 6i, and consequently themove-.

ments of the casing elements 68 and 69 and the electrodes 16 and it withrespect to each other, are controlled by the mechanical low-pass filterarrangement disposed between the housing element 69 and the bottom wall62 of the housing 6|.-

sound energy from being transmitted from the telephone transmitter orfilters out low frequency sound energy. G n the other hand, at high 1*quencies, the mechanical low-pass filter at ment constitutes a rigidconnection between the annular flange 15 carried by the casing element69 and the disk 86, thereby to prevent movement of the casing element 69with respect to the bottom wall 62 of the housing 6| and to causemovement of the casing element 68 with respect to the casing element 69.Accordingly, at high frequencies, the electrodes 10 and H are movedsubstantially with respect to each other. Hence,

the mechanical low-pass filter arrangement does.

not, prevent high frequency sound energy from being transmitted from thetelephone transmitter or permits high frequency sound energy to pass.

From the above description of the mode of operation of the mechanicallow-pass filter arrangement commonly associated with the casing element69 and the bottom wall 62 ofthe housing 6 I, it will be understood thatthe telephone transmitter is effective to transmit at substantialmagnitudes only sound energy having a frequency disposed above a givencut-oif frequency.

Further, it will be understood that the point of cut-off of thetelephone transmitter 60 may be controlled by varying the mass of themetallic rings 11, 18, 19, and 8| and by varying the stiffness of theinsulating rings 82,63, 84 and 85. More particularly, by decreasing thestiffness of the insulating rings 82, 83, 84 and 85 or by decreasing themass of the metallic rings 71, i8, 19, 80 and 8!, the point of cut-oilof the telephone transmitter 60 may be shifted from a given frequencyband to a higher frequency band; on the other hand, by increasing thestiifness of the insulating rings 82, 83, B4 and 85 or by increasing themass of the metallic rings 11, 18, i9, 80 and BI, the point of cut-offof the telephone transmitter 60 may be shifted from a given frequencyband to a lower frequency band. Further it will be understood that anyreasonable number of insulating rings and metallic rings may be providedin the telephone transmitter 60, and that the number of insulating ringsand metallic rings provided will not alone control the point of cutoffof the telephone transmitter 60, as the point of cut-off of thetelephone transmitter will be determined by the product of the compositemass of the metallic rings and the composite stiffness of the insulatingrings.

Referring now to Fig. 5 there is illustrated graphically .twoperformance curves A and B of two telephone transmittersA and B havingeither the general construction of the telephone transmitter II] or thegeneral construction of the telephone transmitter 60. It is noted thatthe telephone transmitter A has a cut-off point occurring between 300and 400 cycles per second; thereby to cause the telephone transmitter Ato transmit a current variation corresponding to a low sound output ofthe order of minus 8 decibels or below in the frequency band below 300cycles per second, and to transmit a current variation corresponding toa high sound output of the order of plus 8 decibels or abovein thefrequency band above 400 cycles per second. On the other hand, thetelephone transmitter 13 has a cut-off point occurring between 700 and800 cycles per second; thereby to cause the telephone transmitter B totransmit a current variation corresponding to a low sound output of theorder of 0 decibels or below in the frequency band below 700 cycles persecond, and to .transmit a current variation corresponding to a highsound output of the order of plus 7 decibels or above in the frequencyband above 800 cycles per second.

A telephone transmitter of the general con struction of the telephonetransmitter l0 and having a performance curve corresponding to theperformance curve A may be altered to have a performance curvecorresponding to the performance curve B by appropriately increasing thestiiiness of the insulating rings or by appropriately decreasing themass of the metallic rings, in the manner previously explained.Similarly, a telephone transmitter of the general construction of thetelephone transmitter 60 and having a performance curve corresponding tothe performance curve A may be altered to have a performance curvecorresponding to the performance curve B by appropriately decreasing thestiffness of the insulating rings or by appropriately decreasing themass of the metallic rings, in the manner previously explained.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is contemplated tocover in the appended claims all such modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. A telephone transmitter comprising a substantially cup-shaped casing,a vibratory diaphragm, means for securing said diaphragm adjacent theperipheral edge thereof in the open end of said casing, first and secondelectrodes arranged in said casing, said first electrode being rigidlyconnected to said diaphragm and movable therewith, said second electrodebeing resiliently connected to said first electrode and movable freelywith respect thereto, a movable mechanical system arranged in saidcasing and including a plurality of spaced-apart mass rings and aplurality of interposed stiffness rings connected together to form acompact bellows-like structure extending between and coupled to saidsecond electrode and said casing, whereby the relative movement betweensaid second electrode and said casing is controlled;' an impedanceele-'" ment, and means governed in accordance with the relativeihdverarirtetweerr"said "first and end of said casing, first and secondsupports arranged in said casing, first and second electrodesrespectively carried by said first and second supports and arrangedin-spaced-apart facing relationship, said first support being rigidlyconnected to said diaphragm and movable therewith, said Second supportbeing resiliently connected to said first support and movable freelywith respect thereto, a movable mechanical system including a pluralityof spaced-apart mass rings and a plurality of interposed stiiiness ringsconnected together to form a compact bellowlilze structure coupled tosaid second support and said casing, whereby the relative movementbetween said second electrode and said casing is controlled, animpedance element disposed between said electrodes, and means governedin accordance with the relative movement between said first and secondelectrodes for controlling the eifective impedance of said impedanceelement, whereby the variation in the effective imperance of saidimpedance element corresponds to sound energy to be transmitted.

3. A transmitter comprising first and second movable electrodes, meansincluding a vibratory member for controlling the movement of said firstelectrode, a support, means including a movable mechanical systemcomprising a plurality of spaced-apart mass rings and a plurality ofinterposed stiflness rings connected together to form a compactbellows-like structure extending between and mechanically coupled tosaid second electrode and said support for controlling the movement ofsaid second electrode, an impedance element, and means governed inaccordance with the relative movement between said first and secondelectrodes for controlling the effective impedance of said impedanceelement.

chanically connected to said diaphragm, whereby the movement of saidfirst electrode is controlled by said diaphragm, a second movableelectrode associated with said first electrode, whereby the sound energytransmitted by said transmitter with said first electrode when said diahragm is subjected to sound waves having low frequencies disposed insaid audible range, whereby the background sound energy is filtered out.

HAROLD C. PYE.

